Population biology including population structure, reproduction, length-weight relationship and condition factor of a commercially important clupeid freshwater fish, Gudusia chapra was studied in the Old Brahmaputra River, Bangladesh during January-December 2009. In the present study, a total of 2032 specimens (1091 male; 941 female) were collected. The overall sex ratio showed significant difference from the expected value 1:1 (male: female = 1:0.86, χ2 = 11.07, p<0.001). Length-frequency distribution showed a size predominance of females over males, where mean female size consistently exceeded that of males throughout the year. Female size at first sexual maturity was estimated as 8.3 cm in standard length (SL). Monthly gonadosomatic index (GSI) was higher during March-September with a peak in April, indicating this was the main spawning season. The allometric coefficient b of the length-weight relationship (LWR) indicated negative allometric growth in males and females, but the analysis of covariance (ANCOVA) showed significant differences in slope and intercept between the sexes (p<0.001). Fulton’s condition factor by months and SLs varied in both sexes and was attributed to variations in GSI with maturity.
The freshwater garfish, Xenentodon cancila (Hamilton 1822), is one of the commercially important, nutritionally valuable food fish in Asian countries, but the natural populations are seriously decreasing due to high fishing pressure and other factors. This study describes the life history traits, including sex ratio (SR), length-frequency distributions (LFDs), length-weight relationships (LWRs), length-length relationships (LLRs), condition factors (Allometric, KA; Fulton’s, KF; relative condition, KR; relative weight, WR) and form factor (a3.0) of X. cancila in the Ganges (Padma) River, northwestern Bangladesh. A total of 175 specimens ranging from 10.50-21.00 cm TL (total length) and 1.44-20.67 g BW (body weight) were investigated in this study. Sampling was done using traditional fishing gears from April 2011 to March 2012. The overall sex ratio showed no significant differences from the expected value of 1:1 (df = 1, χ2 = 0.28, p<0.05), whereas significant difference was found in the LFD (TL) between the sexes (Two tailed, p<0.001). The allometric coefficient b for the LWR indicated positive allometric growth in males, females and combined sexes. The results further indicated that the LLRs were highly correlated. Both KR and KF showed significant variations (Two tailed, p<0.001) between male and female. Also, WR was significantly different from 100 for both sexes (p<0.01), indicating the imbalance habitat with food availability relative to the presence of predators for X. cancila. The calculated values of a3.0 were as 0.0304, 0.0268 and 0.0252 for males, females and combined sexes of X. cancila. This study reports the first complete and comprehensive description of life-history traits for X. cancila from Bangladeshi waters. The data should be useful for the sustainable conservation of this critically endangered fishery in Bangladesh and neighboring countries.
The threatened Reba carp, Cirrhinus reba is a freshwater fish species found in ponds, rivers, canals and tanks of Bangladesh, India, Myanmar, Nepal and Pakistan. The present study describes the first complete and inclusive description of life-history traits including sex ratio, length-frequency distributions (LFD), length-weight relationships (LWR), condition factors (Allometric, KA; Fulton’s, KF; Relative condition, KR; Relative weight, WR), form factor (a3.0) and size at first sexual maturity of C. reba in the Ganges River, NW Bangladesh. Sampling was done using traditional fishing gears including cast net, square lift net and conical trap from April 2011 to March 2012. The total length (TL), fork length (FL) and standard length (SL) were measured to the nearest 0.01 cm using digital slide calipers and total body weight (BW) was measured using an electronic balance with 0.01 g accuracy. The LWR was calculated using the expression: W= a Lb, where W is the BW, L the TL. The size at first sexual maturity of C. reba was estimated using the empirical equation by Binohlan and Froese (2009) for male and female, separately. A total of 250 specimens ranging from 8.00 cm – 23.40 cm TL and 4.30 g – 200 g BW were analyzed in this study. The overall sex ratio did not differ significantly from the expected value of 1:1 (χ2 = 3.38, p< 0.05), but there was significant differences in the TL-frequency distributions (Mann-Whitney U-test, p< 0.001) between male (median = 12.00 cm) and female (median = 15.80 cm). The calculated b for the LWR indicated positive allometric growth (> 3.00) in male and female and there was significant differences in the intercepts (ancova, p< 0.001) and in the slopes (ancova, p< 0.001) between the sexes. In addition, the Mann-Whitney U-test showed significant differences in the Fulton’s condition factor between male and female (p< 0.001). The one sample t-test showed that the mean WR (actual mean = 99.50) did not differ from 100 for male (p= 0.523) and female (p= 0.197) in this study, indicating the habitat was still in good condition for C. reba. Moreover, the size at sexual maturity of male and female C. reba were estimated as 11.50 cm TL and 13.50 cm TL, respectively. The results of this study would be useful for the sustainable conservation of this threatened carp fishery in Bangladesh and also neighboring countries.
The critically endangered catfish eutropiichthys vacha (Hamilton 1822) is one of the commercially high nutritional valuable food fish in Asian countries, but the natural populations are seriously decreasing due to high fishing pressure, leading to an alarming condition and deserving of high conservation importance. Our study describes some biological parameters, including sex ratio, length-frequency distribution (LFD), length-weight relationships (LWRs), length-length relationships (LLRs), condition factors (Allometric, KA; Fulton’s, KF; Relative condition, KR; Relative weight, wR) and form factor (a3.0) of e. vacha in the Jamuna (Brahmaputra River distributary) River, northern Bangladesh. A total of 350 specimens ranging from 8.01-16.95 cm TL (total length) and 1.70-30.38 g BW (body weight) were analyzed in this study. Sampling was done using traditional fishing gears during March 2010 to February 2011. The overall sex ratio showed no significant differences from the expected value of 1:1 (χ2=2.57, p>0.05), and there was no significant difference in the LFD between the sexes (p=0.38). The allometric coefficient b for the LWR indicated isometric growth (~3.00) in males and combined sexes, but negative allometric growth (<3.00) in females. The results further indicated that the LLRs were highly correlated (r2>0.997; p<0.001). KR showed significant variations (F=65.11; p<0.01) between male and female; whereas, KF was not significantly different between the sexes (p=0.64). Also, wR was significantly different from 100 for both sexes (p<0.01), indicating the imbalance habitat with food availability relative to the presence of predators
for e. vacha. The estimated values of a3.0 were as 0.0060, 0.005 and 0.0054 for males, females and combined sexes of e. vacha. This study reported the first complete and comprehensive description of life-history traits for e. vacha from Bangladeshi waters. These results should be useful for the sustainable conservation of this critically endangered fishery in Bangladesh and neighboring countries.